Increasing demand and dependence on the world's crude oil resources portends a grim reality which is exacerbated by the declining availability of those resources. Oil is, and will become even more so, a precious resource the availability of which will be an important determinative of the standard of living in years to come. Crude oil resources are non-renewable. Therefore, an energy intensive world economy will require maximum recovery of oil from the repositories in which it is contained.
Various processes are known for educing oil from hydrocarbon containing solids, such as shale and tar sands using fluidized bed retorting apparatus. Such retorting typically involves hot gaseous products passing upwardly to fluidize a bed of hydrocarbon containing medium, such as tar sands, oil shale and the like. The upwardly flowing gaseous products serve as a sweeping medium for the shale hydrocarbon products which exit the top of a retort. U.S. Pat. No. 4,412,910 to Archer, et al exemplifies such a retorting process. Raw shale is applied to an apparatus wherein gas traveling upward through a fluidized bed of hot raw and spent shale pyrolyzes the raw shale causing its oil and volatile hydrocarbons to rise to the top of the fluidized bed where it is transferred to a gasifier. Oxygen and steam are supplied to the gasifier and react with the carbon of the pyrolyzed shale to produce the desired hydrocarbon by-product. In Archer, et al., the hot gas fluidizes the raw shale in the pyrolyzer apparatus. The hot gas and hot spent shale heat the raw shale while the hot gas acts as a sweeping and transfer medium for the product gas and shale oil components which are subsequently condensed and collected. None of the heat from the product vapors is recovered to provide for process energy requirements in the Archer process.
U.S. Pat. No. 4,087,347 to Langlois, et al shows a shale retorting process in which the solids to be retorted are mixed with a solid heat transfer material to rapidly heat the hydrocarbon containing solids to a high temperature. Langlois discloses that spent retorted shale may be used as the solid heat transfer material. The shale and heat transfer material in Langlois are entrained in a gaseous stream and conveyed upwardly in a gas lift pipe to a retorting vessel in which the hydrocarbon containing solids are rapidly heated so as to vaporize a portion of the hydrocarbons in the solid. The gas and solids in the stream are separated in a disengaging zone in which the partially retorted solids settle to a gravitating bed retort to flow downward countercurrent to the flow of recycle product stripping gas. The upward flow of stripping gas and the gaseous stream from the gas lift are then processed in cyclone separators to separate the product gas from any entrained solids. While Langlois mentions spent shale and product gas recycling, no attempt is made to recover the vast amount of heat in the discarded spent shale or of the heat in the hot flue gases, greatly detracting from the thermal efficiency of the process. Furthermore, a Process such as Langlois discloses does not attempt to collect and use the considerable heat present in the retort product stream.
A method and apparatus for pyrolyzing crushed oil shale of one quarter inch or less is taught in U.S. Pat. No. 3,976,558 to Hall. Hall uses catalytic cracking technology involving fluidizable solids as a heat carrier for achieving pyrolysis of one quarter inch or smaller precrushed raw shale. Pyrolysis vapors exiting from the top of a pyrolyzer of similar design to a conventional catalytic cracker reactor, pass through a vapor cyclone for removing smaller particles or fines and is passed to a fractionator condenser where the vapors are partially condensed and separated into oil and gas. A stream of gas taken from the fractionator is recycled without heat addition, to control fluidization of the countercurrent fluidized bed reactor. Hall makes no attempt to recover the vast amount of heat remaining after the air preheating step. The thermal efficiency embodied in the Hall disclosure leaves much to be desired.
Renewed interest in extracting oil and gas from hydrocarbon containing solids requires that any process for doing so be commercially viable in light of the vast amounts of hydrocarbon containing solids which must be processed in order to yield a relatively small amount of oil and gas product. Although increasing demand for oil and gas may enhance the commercial viability of prior art processes by increasing the value of the oil and gas product, many processes for educing oil and gas from hydrocarbon containing solids according to the prior art are limited in throughput capacity, require a multiplicity of processing units, and further, oil shale retorting and eduction processes and apparatus known in the art are thermally inefficient, requiring that costly amounts of energy be introduced into the process of recovering oil and gas from raw shale, thus diminishing the commercial viability of such processes.